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Human immunodeficiency virus immunity is the natural immunity of humans to HIV. A small percentage of humans are believed to have partial to possible complete immunity to HIV due to mutations in CCR5 receptors. It is estimated that the number of people with some form of immunity to HIV is under 1%. In 1994, Stephen Crohn became the first person discovered to be completely resistant to HIV in all tests performed. He became the basis for multiple anti-viral medications used on HIV-positive patients today. In early 2000, researchers discovered a small group of prostitutes in Nairobi, Kenya who were estimated to have sexual contact with 60 to 70 HIV positive clients a year without signs of infection. Researchers from Public Health Agency of Canada have identified 15 proteins unique to those virus-free prostitutes. Later, however some prostitutes were discovered to have contracted the virus leading Oxford University researcher, Sarah Rowland-Jones, to believe continual exposure as a requirement for maintaining immunity. ==CCR5== C-C chemokine receptor type 5, also known as CCR5 or CD195, is a protein on the surface of white blood cells that is involved in the immune system as it acts as a receptor for chemokines. This is the process by which T cells are attracted to specific tissue and organ targets. Many forms of HIV, the virus that causes AIDS, initially use CCR5 to enter and infect host cells. A few individuals carry a mutation known as CCR5-Δ32 in the CCR5 gene, protecting them against these strains of HIV. In humans, the ''CCR5'' gene that encodes the CCR5 protein is located on the short (p) arm at position 21 on chromosome 3. Certain populations have inherited the ''Delta 32'' mutation resulting in the genetic deletion of a portion of the CCR5 gene. Homozygous carriers of this mutation are resistant to M-tropic strains of HIV-1 infection. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「HIV immunity」の詳細全文を読む スポンサード リンク
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